In a long term evolution advanced (LTE-A, Long Term Evolution Advanced) communication system, a terminal needs to transmit a sounding reference signal (SRS, Sounding Reference Signal) to an evolved NodeB (eNB, E-UTRAN NodeB) to help the eNodeB obtain uplink channel information, so as to implement functions, such as frequency selective scheduling and link adaptation.
In a multi-antenna transmitting mode, the eNodeB needs to measure each antenna port of the terminal. Therefore, each antenna port sends an SRS periodically, which inevitably leads to insufficiency of SRS resources. In fact, in many cases, the terminal does not need to keep sending the SRS all the time. Therefore, in the prior art, it is proposed that sending the SRS dynamically and non-periodically is used to reduce resource requirements. That is, the eNodeB determines whether a terminal needs to send the SRS according to actual conditions. If the terminal needs to send the SRS, the eNodeB sends trigger information through a physical downlink control channel (PDCCH, Physical Downlink Control Channel) to instruct the terminal to send the SRS. After triggered, the terminal sends the SRS according to resource information. The resource information includes SRS sending time, a frequency band position occupied by the SRS, a bandwidth, a cyclic shift (CS, Cyclic Shift), a comb, and so on.
Currently, there are mainly two methods for obtaining resource information. A first one is that the eNodeB carries the resource information in a trigger command when delivering the trigger command to the terminal; and a second one is that the eNodeB presets an SRS resource pattern (hereinafter referred to as resource pattern) for each terminal through higher-layer signaling, and when the terminal is triggered, the terminal finds proper resource information in the resource pattern according to trigger time, and then uses the resource information to send the SRS. Because the resource information involves many parameters, if the first method is adopted, PDCCH load is high. Therefore, in the prior art, the second method is mainly adopted to obtain the resource information.
Adopting the second method may reduce the PDCCH load, but it is not flexible. For example, if a bandwidth in the preset resource pattern is narrow, when a wide frequency band is measured, the SRS needs to be sent for many times to cover the frequency band that needs to be measured, which leads to high PDCCH overhead and long measurement delay; if a bandwidth in the preset resource pattern is very wide, when a narrow frequency band is measured, a frequency band that needs no measurement originally is also covered by a sent SRS, which leads to a waste of resources.